back muscle rehab

I started the sslp about 2 months ago with all sorts of errors but it still took my squat from 205x5x3 to 295x5x3 (kinda) doing my 295 sets last Monday I pulled a back muscle because my back rounded out just out of the trap on the second set of the last set. That was Monday and today, friday, (I was still unable to bend forward without pain on Wednesday so I skipped) I went with a nice long warm up until I hit 135 when I was unable to perform the squat without pain. Specifically the lowbar squat, with proper lean over there was pain, but keeping a very verticle back angle was painless. Another problem I encountered was that during the walk back to take my stance when I had to relax my trunk muscles to breath it was the most painful. I moved on to the press next, and it was only noticeable during the hip thrust at the beggining. Then deadlifts where I could feel the muscle being worked pain free but with some soreness.

If this is a muscle belly injury consider using the Starr rehab protocol. I did this recently after straining a back muscle. I alternated squats and deadlifts for the protocol.

Also, Are you using a belt? If not, get one.

If the Starr protocol isn't appropriate, start with a weight you can tolerate and titrate volume and intensity to make sure you feel at least a little better by the next time you squat. If you feel worse, you did too much last time.

If none of that works you might need to get looked at (bet it will work, though).